On Mon, Aug 02, 2021 at 12:04:58PM +0800, Matt Johnston wrote:
> Allows attaching multiple child busses in a mux topology
> to an mctp-i2c instance on the root bus. In general I2C
> slave mode does not make sense for mux busses, but the MCTP
> request/response protocol means the the root can switch
> between child muxes for incoming I2C messages.
Perhaps a diagram of what I2C buses look like would help because I don't
understand this.
>
> Signed-off-by: Matt Johnston <matt@xxxxxxxxxxxxxxxxxxxx>
> ---
> .../devicetree/bindings/net/mctp-i2c.yaml | 42 +++++++++++++++++--
> 1 file changed, 38 insertions(+), 4 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/net/mctp-i2c.yaml b/Documentation/devicetree/bindings/net/mctp-i2c.yaml
> index f9378cd845d4..45429cbcc6a1 100644
> --- a/Documentation/devicetree/bindings/net/mctp-i2c.yaml
> +++ b/Documentation/devicetree/bindings/net/mctp-i2c.yaml
> @@ -12,11 +12,10 @@ maintainers:
> description:
> The MCTP I2C binding defines an MCTP endpoint on the I2C bus to
> communicate with I2C peripherals using MCTP (DMTF specification DSP0237).
> -
> - An mctp-i2c device must be attached to a hardware bus adapter which supports
> + A single binding node can attach to multiple child busses in a mux topology.
> + An mctp-i2c node's parent must be a hardware bus adapter which supports
> slave functionality. The reg address must include I2C_OWN_SLAVE_ADDRESS.
>
> -
> properties:
> compatible:
> const: mctp-i2c
> @@ -24,6 +23,17 @@ properties:
> reg:
> maxItems: 1
>
> + bus-attach:
> + $ref: "/schemas/types.yaml#/definitions/phandle-array"
> + description: |
> + List of phandles of I2C busses to attach to. I2C mux busses may only
> + be attached to an mctp-i2c binding on their parent root adapter in the
> + mux topology.
> + If no bus-attach property is specified then only the direct parent
> + I2C bus is attached. Otherwise to include a direct parent bus it
> + must be included in the bus-attach list if needed.
> +
> +
> additionalProperties: true
>
> required:
> @@ -33,12 +43,36 @@ required:
> examples:
> - |
> #include <dt-bindings/i2c/i2c.h>
> - i2c {
> +
> + // simple attaching to a root adapter i2c0
> + i2c0: i2cbus0 {
> + #address-cells = <1>;
> + #size-cells = <0>;
> +
> + mctp@50 {
> + compatible = "mctp-i2c";
> + reg = <(0x50 | I2C_OWN_SLAVE_ADDRESS)>;
> + };
> + };
> +
> + // attaching to a root adapter i2c5 and a child mux bus i2c14
> + i2c5: i2cbus5 {
> #address-cells = <1>;
> #size-cells = <0>;
>
> mctp@50 {
> compatible = "mctp-i2c";
> reg = <(0x50 | I2C_OWN_SLAVE_ADDRESS)>;
> + attach-bus = <&i2c5 &i2c14>;
> };
> };
> +
> + i2cmux0 {
> + compatible = "i2c-mux-gpio";
> + #address-cells = <1>;
> + #size-cells = <0>;
> + i2c-parent = <&i2c0>;
> + i2c14: i2c@5 {
This is not how "i2c-mux-gpio" works. First you are missing mux-gpios.
Second, how is this a mux with only 1 mux selection as the child nodes
are the I2C buses for each mux selection.
> + reg = <0>;
Either reg should be 5 here or the unit-address should be 0.
> + };
> + };
> --
> 2.30.2
>
>
